Page 80 - Industrial Wastewater Treatment, Recycling and Reuse

Industrial Wastewater Treatment, Recycling, and Reuse: An Overview 57

In recent years, the sustainability of the industry has been threatened because
of not meeting pollution standards. It is imperative that the industry sector
implement proper effluent treatment methods, not just to reduce pollution,
but also to contribute to reducing water stress through water recycling
and reuse.

1.5.3 Food Industry

One important industry sector that conventionally uses biological methods
of treatment, mostly activated sludge processes, is the food industry. This is
typically a seasonal industry, and therefore there is no regular generation of
wastewater throughout the year similarly to the chemical industry. Further,
wastewaters generated differ significantly in the type of pollutant, concen-
tration, and volume, depending on the nature of food processing and
manufacturing. The wastewater from this industry emanates a foul odor
and has somewhat high BOD, of the order of 400 mg/L or higher. For
the starch processing industry, BOD and COD are significantly higher, of
the order of 10,000 and 20,000 mg/L respectively. Important food indus-
tries include brewery and beverages; vegetable oil–producing industries;
the dairy industry, producing milk and milk derivatives such as cheese
and butter; the starch industry; and the confectionary industry. Oil is also
the main pollutant in the wastewaters of the vegetable oil and starch indus-
tries; this needs to be removed prior to biological treatment. Slaughterhouses
and the meat-processing industry belong to a different class that produces
wastewater with biological material such as blood containing pathogens,
hormones, and antibiotics. The problem of finding antibiotics in sewage
wastewaters because of improper disposal in cities is also approaching signif-
icant proportions and requires careful attention because the desired concen-
trations for many of these pollutants are below picogram levels. The
wastewater volume generated in the beverage industry is believed to be
3 3
10 m per ton product, for milk and the dairy industry 10-20 m waste-
water per ton of product, while the wastewater volume in brewery industry
3
such as beer production is of the order of 10–30 m water per ton of product
(Examples of food processing wastewater treatment, www.env.go.jp/earth/
coop/coop/document/male2_e/007.pdf). The BOD level in wastewater is
also an order of magnitude higher in the brewery industry as compared to
that in the beverage industry. In general, the treatment methodology follows
the following steps:
1. Preliminary treatment for the removal of oils/solids
2. Aerobic/anaerobic treatment